The present invention relates to a method of establishing actual changes and intended changes of a spatial angle of a sensor or effector axis attached to a receiver directly rotatable around a first axis and indirectly rotatable around at least one additional axis. The invention is also directed to a device useful in performing the method.
As an example, but without any restrictive effect, in the following the problem upon which the present invention is based is to be described with reference to a tracking device, such as a tracking device having a sensor or effector, the tracking device being positioned on a movable mounting surface, such as a vehicle or ship deck. For example, the sensor may be an image recording device and the effector may be a weapon barrel of an artillery weapon, the main optical axis of the image recording device and/or the core axis of the weapon barrel able to be considered at least approximately the main axis. The sensor and/or effector is to be movable in such a way that its alignment and/or the alignment of its main axis is always correlated with the position of an external object which moves in relation to the sensor and/or effector and thus follows the object; in the case of a sensor, this means that it is always pointed directly at the moving target, while in the case of an effector implemented as a weapon barrel, this generally means that it is pointed at a point which the object only reaches later, so that the projectile fired from the weapon barrel hits the object at the point cited.
The sensor and/or effector is rigidly attached to a receiver, together with which it essentially forms one actual functional unit. The receiver is rotatably connected to a carrier via an axis of elevation; the elevation of the sensor and/or effector may be set essentially through a rotation of the receiver in relation to the carrier around the axis of elevation; it is assumed that the main axis runs horizontally in the rest position. The carrier is rotatably connected to a carrier base via a roll axis; the effect of a rolling movement may be compensated for through a rotation of the carrier in relation to the carrier base around the roll axis in such a way that the axis of elevation remains horizontal or deviates only briefly by a small value from the horizontal; the roll axis is perpendicular to the axis of elevation and at an angle of 60° to a lateral axis, for example. The carrier base is rotatably connected via the lateral axis, directly or indirectly, to the vehicle and/or ship deck; the lateral angle of the sensor and/or effector may essentially be set through a rotation of the carrier base around the lateral axis; the lateral axis is at least approximately vertically aligned in the rest position.
The directions and/or angles of the various axes of rotation indicated above are theoretical values which one attempts to maintain. The actual values of these directions and/or angles generally deviate from the theoretical values. The deviations are essentially based on the permissible manufacturing and mounting tolerances, in that relative movements generally do not occur precisely continuously but rather in steps, if small steps, and also on changes of the relative positions of the centers of gravity of individual elements of the tracking device during their movements. The results of the deviations and/or geometry errors cause the actual direction of the main axis of the sensor and/or effector to deviate from the theoretical and/or desired direction by a—generally spatial—angular error. In other words, during rotations around the axes of rotation, the actual changes of specific angles deviate from the intended changes of these angles. The intended changes are provided in this case by a coder device. The deviations of the actual changes from the intended changes is referred to as angular errors. The angular errors have an influence on the results of the functional unit, for example, on the precision with which a sensor measures an object.
The angular errors are generally established at the factory in the course of a testing method, in the scope of a quality check, for example. The angular errors are typically different for the individual tracking devices and/or tracking device types and therefore at least partially describe the individual tracking devices. The angular errors are stored for this purpose.
The angular errors are not to exceed certain limiting values. They may be compensated for, which may be performed either through hardware and/or apparatus by reworking and/or mounting corrections, or through software, by taking the angular errors established into consideration, for example in the analysis of the results of a sensor system.
Independently of whether the angular errors are only stored or whether they are compensated for, they must be measured.
For the measurement of such angular errors typical until now, a chain measurement has been performed. For this purpose, first leveling is performed, and subsequently measurement from one axis to the next, i.e., from the lateral axis to the roll axis and further to the axis of elevation, is performed step-by-step. Optical measuring devices are mainly used for this measurement, such as autocollimators, theodolites, mirrors, angle levels, and inclinometers. In addition, multiple adapters, holders, carriers, and equivalent masses are necessary. The multiple means necessary, their differing resolution and measurement precisions, and the necessity of working very precisely are disadvantages of the typical measurement method. However, its greatest disadvantage is that measurement errors accumulate due to the chain measurement and coupling errors are practically unavoidable.
It is therefore the object of the present invention,    to specify a method of the type initially cited, using which the disadvantages of the typical method may be avoided;    to provide a device of the type initially cited, which allows problem-free performance of the method; and    to suggest a use of the device.